Aircraft gas turbine engines include various tubes for carrying bleed air, fuel, and oil for various purposes. In the bleed air system for example, suitable metal tubes such as Inco 625 tubes are used for carrying the relatively hot compressor bleed air to various parts of the engine. The tubes must be suitably mounted at spaced apart locations to stationary mounting supports, and configured for minimizing vibration thereof caused by excitation forces being generated in the operating engine.
In order to minimize vibratory friction wear between the bleed air tubes and their mounts, conventional wear sleeves are typically used and interposed between the outer circumference of the tube and the complementary clamp which rigidly secures the tube to its mounting support. A typical wear sleeve is tubular in configuration and may be fully annular in which case it is initially axially assembled over an open end of the tube, or may be formed in two semi-circular parts and assembled together around the tube. Conventional wear sleeves are typically brazed or welded to the parent tube, and in the case of Inco 625 tubes, the brazed alloy is either nickel or gold. Nickel is relatively brittle and gold is very expensive. Welding and brazing are both time consuming processes and require inspection after completion for ensuring adequacy of the assembly. Both processes also leave stress concentrations at the wear sleeve ends and horizontal split lines for example. Since the tube is mounted in a dynamic environment in the gas turbine engine, vibratory excitation forces generate stress at the wear sleeve support. This stress must be maintained suitably low in magnitude for obtaining a useful life of the tube.